When trying to help users, not only new ones, with their build there's a lot to take into consideration. The most important thing is what the user wants to do. What kind of player they want to build. There's also always more than one attribute you have to keep in mind. Maxing one attribute and dismissing the rest isn't gonna get you anywhere. No matter how important that one attribute is. I'd give the user a few options so that they themselves can decide which attribute to go with depending on their own goals.

Offensive
If the user wants to be an offensive powerhouse. Then the two main attributes to focus on would be Offensive Read and Getting Open. These two attributes decides how offensively smart the player is, and also how good they are and getting into a good position. Build these two attributes guarantees that your player will be a great offensive presence. Whether the user decides they want to be a playmaker, sniper or screener. These two attributes is the foundation they need.

Defensive
Similarly to the offensive attributes. Two key defensive attributes for anyone wanting to become a defensive player, be it defenseman or defensive forward, is the "know what" and "know how" attributes. Defensive Read and Positioning. These attributes are vital to any defensive player. And are also great to focus on no matter what. Even if you haven't figured out what kind of defensive player you want to be. Building up these two attributes makes sure you will be a nuisance to any opposition. While also giving you the option to branch out into a Kronwall or a Karlsson. Or anything else.

General
If they haven't yet decided on their player archetype, there are other attributes a user can focus on without throwing points into attributes that they may later regret. In the list of physical attributes we have a handful that are useful to any and all players. Except Fighting, of course. Any player needs to be a good skater, have good conditioning, and be strong. Even if you can blow out a candle light with a puck from 500 feet away. If you're slow, weak or lazy, you'll never get the chance to do so.

As mentioned, almost all physical attributes are critical. But if I were to name two that stand out, they would be Stamina and Strength. Stamina is a given. If you only have the energy to play one period every game, you're gonna be a liability most of the time. You need to be able to handle a full game, plus OT. And with the amount of back-to-backs we have nowadays. Stamina is more important than when we first started using FHM. Strength on the other hand has always been important. It helps most part of your game. And is probably the main all-around skill. It helps your game no matter how you play and should be a priority throughout your player's career. If you don't know what to update, I recommend Strength.

Honorable mention: Puckhandling